chapter 3 - RiuNet

GENERAL INTRODUCTION
3. Sperm quality in fish
From an aquacultural point of view, breeding in captivity of some marine
species is a key factor in reaching reproductive success, and the main
limitations are the quantity and quality of male and female gametes.
However, until recently gamete quality has not received much attention,
and only a few studies have been published about the effect of specific
factors on gamete quality (see review Bobe and Labbé, 2000). Traditionally,
hatcheries have focused more on the quality of eggs and larvae rather than
that of sperm, even though sperm quality also affects the performance of
larvae production (Trippel and Nielson, 1992). In fact, sperm in commercial
hatcheries is often inadequate both in terms of quantity and quality and
often optimal fertilisation rates are not reached through in vitro fertilization
trials (Rurangwa et al., 2004). Therefore, it appears that the assessment of
sperm quality would be a useful tool that could be applied in a wide range
of reproduction fields, and several factors such as artificial fertilization,
chilled storage, cryopreservation or even the effect of environmental
pollutants on fish reproductive success could be improved by sperm quality
evaluation (Cabrita et al., 2005a; Fabroccini et al., 2010).
First of all, it seems essential to define and understand what sperm quality
means. From a biological standpoint, sperm quality could be defined as the
ability ofthe spermatozoa to reach and fertilize the oocyte (Fauvel et al.,
2010). In this respect, any quantifiable parameter directly correlated with
the fertilization capacity could potentially be used as a sperm quality
indicator. Sperm is the final result of a maturation process in which several
haploid cells are produced with the aim of transmitting paternal genetic
information to the next generation. It is important to highlight that
throughout this process, several factors can affect the sperm quality and
thus, fertilization success. The most important factors are displayed in Table
1, all of different origins, from the reproductive age of the breeder to the
hormonal treatment (if required) applied to achieve artificial maturation.
Therefore, in order to achieve good quality sperm it is essential to take all
these factors into account, because slight variations in any of them could
negatively affect the sperm quality and thus, decrease fertilization success.
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